Argatroban formulation

ABSTRACT

An aqueous, stable, sterile pharmaceutical composition of the thrombin inhibitor argatroban in a solution containing an acid to solubilize the argatroban, substantially free from dehydrated alcohol is described, as well as a method for its preparation.

BACKGROUND OF THE INVENTION

The present invention relates to a new pharmaceutical formulation of1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate,commonly known by the generic name “argatroban.” Argatroban is asynthetic direct thrombin inhibitor derived from L-arginine and is auseful anti-coagulant agent.

Argatroban is considered slightly to very slightly soluble in wateraccording to the USP classification of solutes, with solubility on theorder of 0.8 to 0.9 mg/mL. It is also both light and heat-sensitive andtends to degrade unless stabilized. Argatroban is commercially availablein concentrated form in an aseptically-filled vial containing, per mL,100 mg argatroban, 750 mg D-sorbitol and 1000 mg dehydrated alcohol.When administered to a patient, this formulation is diluted to aconcentration of 1.0 mg/mL in an admixture diluent solution containingan osmotic agent such as sodium chloride or dextrose (c.f. U.S. Pat. No.5,214,052).

Other formulations of argatroban are described in U.S. Pat. Nos.5,679,690 and 6,087,375, European Patent Applications 0,565,897 A1 and0,621,036 A1 and WO 2005/009361 A2.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an aqueous, stable, sterilepharmaceutical composition of a thrombin inhibitor suitable forparenteral administration, substantially free from dehydrated alcoholand having a pH between 3.5 and 8.5 comprising in solution 0.1 to 10mg/mL 1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban) and an acid to solubilize the argatroban. This compositionmay optionally further contain a buffering agent to help maintain pH andan osmotic-adjusting agent to enhance infusion properties. Thecomposition is storage-stable (both light and heat), capable of beingaseptically-filled and heat-sterilized, and contains argatroban in arange of concentrations, from a ready-to-use concentration to aconcentrate that requires dilution prior to administration. In a furtheraspect of the present invention a method is provided for preparing theaforementioned formulation of argatroban in a sealed container, such asan ampoule, vial, syringe or infusion bag, and autoclaving for a periodof time sufficient to render the composition sterile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of the effect of pH on argatrobancontent as function of time (weeks) stored at 55° C.

FIG. 2 is a graphical representation of solution stability for 1 mg/mLargatroban injection under various temperature conditions as a functionof time.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a sterile, stable parenteral compositioncontaining argatroban with enhanced aqueous solubility and optionally apharmaceutically acceptable buffering agent and an osmotic adjustingagent to adjust the tonicity of the solution. The composition ispackaged in a sealed container that may either be aseptically-filled or,preferably, subjected to terminal sterilization to reduce themicrobiological burden of the formulation. The present invention isstable against hydrolytic degradation and other adverse chemicalreactions, and when packaged appropriately, for example, with analuminum overpouch, against photolytic degradation.

The enhanced solubility of argatroban in aqueous solution isaccomplished by the addition of an acid. The acids will typically bedilute, meaning on the order of 0.01 to 3 N. Though not wishing to belimited to any one theory, it is believed that the acid (which may beeither organic or inorganic) forms an “ionic liquid” or in-situ saltsolution of argatroban. This refers to an ionic liquid and counter ionof salt where the ions are poorly or randomly arranged and/orcoordinated. The ionic liquid/in-situ salt solution may have ions withdelocalized charge states, or resonance in the drug molecule that hasbeen stabilized by its counter ion. The effect is that stable solutionsof argatroban having solubilities ranging from 0.1 to 10 mg/mL, morecommonly 0.8 to 10 mg/mL are possible in spite of being substantiallyfree of solvent or additional solubilizing and/or stabilizing agents,such as ethanol, saccharides, surfactants, long chain fatty acids,cyclodextrin derivatives, caffeine. The solution is thermodynamicallystable at room temperature for at least 24 months with essentially nosignificant degradation and remains within the appropriate pH range.

Table I provides a summary of enhanced solubility of argatroban indilute acids. TABLE I Solubility of Argatroban in dilute acids at roomtemperature Dilute acids¹ Visual Dissolution² Amount (mg/mL)³ Phosphoricacid Freely soluble ≧10.08 Acetic acid Very soluble ≧11.5 Tartaric acidFreely soluble ≧10.4 Citric acid Moderately soluble ≧9.79 Formic acidVery soluble ≧10.08 Maleic acid Moderately soluble ≧9.32 Hydrochloricacid Moderately soluble ≧10.1¹The molarity of the acids used were ˜1-3 N²Classification according to Remington's Pharmaceutical Science, 20^(th)edition³Amount of argatroban was determined by HPLC method

“Stable”, as used in the context of this application, means remaining ina state or condition that is suitable for administration to a patient.Formulations according to the present invention are found to be stablewhen maintained at room temperature for at least 24 months, and aregenerally stable at room temperature for 24 to 36 months.

A “sterile” composition, as used in the context of this application,means a composition that has been brought to a state of sterility andhas not been subsequently exposed to microbiological contamination, i.e.the container holding the sterile composition has not been compromised.Sterile compositions are generally prepared by pharmaceuticalmanufacturers in accordance with current Good Manufacturing Practice(“cGMP”) regulations of the U.S. Food and Drug Administration.

The product can take the form of a sterile, stable, ready-to-useformulation for infusion. This avoids the inconvenience of diluting aconcentrated argatroban small volume parenteral formulation intoinfusion diluents prior to infusion, as well as eliminates the risk ofmicrobiological contamination during aseptic handling and any potentialcalculation or dilution error. Such formulations, not being preparedfrom a concentrate, will be essentially free from saccharide component,e.g. D-sorbitol, and dehydrated alcohol component, e.g. dehydratedethanol. The product can also take the form of a concentratedformulation which must be diluted prior to administration.

The aqueous, sterile, stable pharmaceutical composition of the presentinvention is suitable for parenteral administration to a patient. Forexample, the composition may be administered in the form of a bolusinjection or intravenous infusion. Suitable routes for parenteraladministration include intravenous, subcutaneous, intradermal,intramuscular, intraarticular, and intrathecal. The ready-to-useformulation of the invention is preferably administered by intravenousinfusion.

Containers suitable according to the present invention are those knownin the art. They include vial, syringe, infusion bag, bottle and ampoulepresentations. Containers may be fabricated from glass or from polymericmaterials. Ready-to-use formulations are typically packaged in vials,syringes, infusion bags and bottles, while concentrated formulations aretypically packaged in ampoules.

The composition of the present invention can be lyophilized by knowntechniques, and subsequently reconstituted prior to administration.Certain acids in the composition, such as acetic acid, may be volatileand partially lost during lyophilization. In these cases, they must bereplenished in the reconstituted solution.

The effect of pH on the degradation of argatroban is studied in fiveaqueous buffers at 55° C. All buffer solutions are prepared in Water forInjection, in accordance with USP standard buffer solutions. Five buffersolutions are prepared at pH 2.01, 5.0, 7.4, 8.02 and 11.05. For eachlevel, 1 mg/mL of argatroban is accurately weighed and transferred to acalibrated flask. The buffer solution is added to the flask withadequate mixing to dissolve completely, and then diluted to volume.Samples of all five solutions are stored in amber glass (for protectionfrom light) and held at 55° C. Samples are pulled at pre-determinedintervals and then analyzed for pH, potency and the physical appearanceof the solutions.

The concentration of the drug is determined by a high performance liquidchromatographic (HPLC) method. The data obtained is plotted as a log ofdrug concentration versus time with the assumption that the ratereaction is apparent first-order (k_(observed)). Degradation rate of theargatroban at accelerated temperature of 55° C. versus various pH valuesis monitored and a pictorial representation is shown in FIG. 1. Thek_(observed) is calculated from the slopes of the linear regressionlines, and maximum changes in the degradation rate are both at low andhigh pH values of (pH 2.0 and 11.05). The lowest k_(observed) in thisstudy is seen in the range from pH 5.0 to about pH 8.0, suggesting thatthe pH of the composition should be controlled for maximum stability.The results indicate that the pH should be between 3.5 and 8.5,preferably between 4.5 and 6.5, more preferably about 4.5 to 5.5. The pHcan be adjusted as known in the art by addition of sodium hydroxide oracetic acid.

The ready-to use formulation of argatroban injection is subjected tostress studies to predict the shelf life of the product in aqueousmedia. Solutions of argatroban composition after autoclave cycle of 121°C. for 20 minutes with minimal degradation are stored at 25° C., 40° C.and 55° C. (protected from light) for a six-month period. The pH,potency, particulate matter and the physical appearance of the solutionsare determined. The concentration of the drug is determined by a highperformance liquid chromatographic (HPLC) method. Data obtained fromthis study indicate that the stabilization effect is maximized at pH5.0±0.5 and the total degradants change over the period studied at 40°C. is less than 1%. Regression and extrapolation of the stability dataobtained suggests a shelf life of aqueous composition of not less than24 months at room temperature (25° C.). FIG. 2 is a plot of solutionstability for 1 mg/mL argatroban injection under various temperatureconditions as a function of time.

Moreover, it has been determined that no buffering agent is necessarywhen the argatroban composition of the present invention is stored incertain types of containers since the argatroban composition isinherently stable. Suitable such containers are those whose surfaces incontact with the argatroban composition do not contain leachablesubstances, which are typically alkaline. One such suitable container isBaxter Healthcare Corporation's IntraVia® flexible plastic container.The pHs of the compositions in the case where no buffering agent is usedwill generally range from about 4.5 to 5.5.

Argatroban is present in the present composition in an amount rangingfrom 0.1 to 10 mg/mL. Ready-to-use formulations may contain 0.5 to 10mg/mL, more commonly about 1 mg/mL argatroban.

Acids used to solubilize the argatroban may be organic or inorganic.Suitable such acids include phosphoric acid, acetic acid, tartaric acid,citric acid, formic acid, malic acid, hydrochloric acid and mixturesthereof. They are typically employed in the solution at concentrationsranging from 0.01 to 3 N, depending on the degree of ionization andassociation of the counter-ion stability in an aqueous environment. Thepreferred acid is acetic acid, and will be present in an amount rangingfrom 0.5 to 6 mg/mL.

Suitable physiologically-acceptable buffering agents include acetate,glutamate, citrate, tartrate, benzoate, lactate, malate, gluconate,phosphate and glycine, with acetate being preferred. The preferredbuffering system comprises a combination of sodium acetate and aceticacid. Buffering agents are present in the composition in a concentrationthat depends from the concentration of argatroban. The concentrationwill typically range from 0.05 to 200 mM, and from 10 to 100 mM forformulations containing 0.5 to 10 mg/mL argatroban.

Suitable osmotic-adjusting agents, when used, are compatible with the pHrequirements of the present formulation, and include one or more ofsodium chloride, calcium chloride, potassium chloride, dextrose andsodium lactate. Preferred are sodium chloride and dextrose. Theformulations of the present invention may contain 1 to 100 mg/mLosmotic-adjusting agent; preferably 4 to 60 mg/mL sodium chloride, morepreferably 4 to 10 mg/mL sodium chloride; or dextrose at a level nogreater than 5% (weight by weight), typically in an amount ranging from25 to 60 mg/mL.

Compositions according to the present invention can be prepared intosmall volume parenteral (SVP) and large volume parenteral (LVP) dosageforms. The dosage forms can be held in any suitable container. Suitablecontainers include, for example, glass or polymeric vials, ampoules,syringes or infusion bags with sizes ranging from 1 ml to 500 ml. SVPready-to-use solutions are typically filled into ampules and vials in 1to 100 mL presentations. In addition, syringes can be used as thecontainer for a ready-to-use SVP, which are sold as “pre-filledsyringes”. The LVP presentations can be contained in infusion bags orbottles.

Polymeric containers are preferably flexible and can contain or be freeof polyvinylchloride (PVC). Preferred containers are free of PVC, suchas those disclosed in U.S. Pat. Nos. 5,849,843 and 5,998,019. Polymericcontainers can further be provided with a moisture barrier as asecondary packaging system to prevent the loss of water during storageand to further ensure the stability of the formulation. A preferredmoisture barrier is an aluminum overpouch, which will also protect theformulation from photolytic degradation.

Procedures for filling compositions of the present invention incontainers, and their subsequent processing are known in the art. Theseprocedures are used to produce sterile pharmaceutical drug productsoften required for health care. Such processing techniques preferablyuse a sterilization process to destroy or eliminate any microorganismsthat may be present in the argatroban formulations followingpreparation. For example, terminal heat sterilization can be used todestroy all viable microorganisms within the final, sealed container ofthe argatroban formulation. An autoclave is commonly used to accomplishterminal heat-sterilization of drug products in their final packaging.

Typical autoclave cycles in the pharmaceutical industry to achieveterminal sterilization of the final product are 121° C. for 15 minutes.The argatroban composition of the present invention can be autoclaved ata temperature ranging from 115 to 130° C. for a period of time rangingfrom 5 to 40 minutes with acceptable stability. Autoclaving ispreferably carried out in the temperature range of 119 to 122° C. for aperiod of time ranging from 10 to 36 minutes.

Alternatively, sterile pharmaceutical compositions according to thepresent invention may be prepared using aseptic processing techniques.Aseptic filling is ordinarily used to prepare drug products that willnot withstand heat sterilization, but in which all of the ingredientsare sterile. Sterility is maintained by using sterile materials and acontrolled working environment. All containers and apparatus aresterilized, preferably by heat sterilization, prior to filling. Thecontainer (e.g., vial, ampoule, infusion bag, bottle, or syringe) arethen filled under aseptic conditions.

The following examples further illustrate the invention but should notbe construed as in any way limiting its scope. In each case, a 1 mg/mLformulation is prepared.

EXAMPLE 1

Argatroban 1 mg Acetic Acid, USP 0.546 mg Sodium Acetate Trihydrate, USP2.8 mg NaCL, USP osmotic adjusting agent 5.9 mg Acetic acid or NaOH Toadjust pH as required Water for Injection, USP q.s. Autoclave cycle =121° C., for 2 to 20 minutes

EXAMPLE 2

Argatroban 5 mg Acetic Acid, USP 0.546 mg NaCL, USP osmotic adjustingagent 5.9 mg Acetic acid or NaOH To adjust pH as required Water forInjection, USP q.s. Autoclave cycle = 121° C., for 2 to 20 minutes

EXAMPLE 3

Argatroban 1 mg Phosphoric Acid, USP 8.5 mg Sodium Phosphate 1.8 mgNaCL, USP osmotic adjusting agent 5.9 mg Acetic acid or NaOH To adjustpH as required Water for Injection, USP q.s. Autoclave cycle = 121° C.,for 2 to 20 minutes

EXAMPLE 4

Argatroban 10 mg Hydrochloric acid 0.146 mg NaCl, USP osmotic adjustingagent 5.9 mg HCl or NaOH To adjust pH as required Water for Injection,USP q.s. Autoclave cycle = 121° C., for 2 to 20 minutes

EXAMPLE 5

Argatroban 1 mg Tartaric Acid, USP 12.3 mg NaCl, USP osmotic adjustingagent 5.9 mg Tartaric acid or NaOH To adjust pH as required Water forInjection, USP q.s. Autoclave cycle = 121° C., for 2 to 20 minutes

EXAMPLE 6

Argatroban 5 mg Critic Acid, USP 15 mg Sodium Citrate 1.2 mg NaCl, USPosmotic adjusting agent 5.9 mg Critic Acid, or NaOH To adjust pH asrequired Water for Injection, USP q.s. Autoclave cycle = 121° C., for 2to 20 minutes

EXAMPLE 7

Argatroban 1 mg Acetic Acid, USP 0.546 mg Sodium Acetate Trihydrate, USP2.8 mg Dextrose, USP osmotic adjusting agent 50 mg Acetic acid or NaOHTo adjust pH as required Water for Injection, USP q.s. Autoclave cycle =121° C., for 2 to 20 minutes

EXAMPLE 8

Argatroban 5 mg Acetic Acid, USP 0.546 mg Sodium Acetate Trihydrate, USP2.8 mg (No osmotic adjusting agent) Acetic acid or NaOH To adjust pH asrequired Water for Injection, USP q.s. Autoclave cycle = 121° C., for 2to 20 minutes

EXAMPLE 9

Argatroban 5 mg Formic Acid, USP 3.6 mg NaCl, USP osmotic adjustingagent 5.9 mg Formic acid or NaOH To adjust pH as required Water forInjection, USP q.s. Autoclave cycle = 121° C., for 2 to 20 minutesProcedure

The equipment and glassware for compounding, filtering, and filling areproperly washed and depyrogenated. The filter assembly, filling tubeassembly, and other parts and equipment are sterilized.

Eighty percent (80%) of the final volume of cool Water for Injection iscollected in a calibrated compounding tank. Sodium chloride is added tothe tank and the solution is stirred until sodium chloride is dissolved.Sodium acetate is then added to the tank, stirred until all excipientsare dissolved. The tank is adjusted to 90% of final volume with Waterfor Injection and mixed. Approximately 1.08 grams of acetic acid isadded 2 liter of water to prepare of a slurry solution of argatroban.Argatroban is weighed into the 2 liter acidified water to form a slurrysolution. This slurry is then added to the compounding tank and thesolution is mixed. The solution is then adjusted to pH 5.5 with 1 Nsodium hydroxide or acetic acid if necessary. The solution is brought tofinal volume with Water for Injection and mixed.

The solution is then filled into 250 ml non-PVC flexible bags (IntraVia®flexible plastic container (PL 2408-3 non-PVC multi-layer plastic film)with one standard PL 146.RTM. PVC membrane tube, one PL 2409-3multi-layer plastic co-extruded administration port tube, one PL 141 PVCblue-tip closure (administration port protector), available from BaxterHealthcare Corporation). These bags are sealed in aluminum foiloverpouches. The products are then loaded into an autoclaving sterilizerand sterilized at 121° C. for 20 minutes.

1. An aqueous, stable, sterile pharmaceutical composition of a thrombininhibitor suitable for parenteral administration, substantially freefrom dehydrated alcohol and having a pH between 3.5 and 8.5 comprisingin solution: a. 0.1 to 10 mg/mL1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban); and b. an acid to solubilize the argatroban.
 2. Thepharmaceutical composition of claim 1 further comprising: c. a bufferingagent.
 3. The pharmaceutical composition of claim 1 further comprising:d. an osmotic-adjusting agent.
 4. The pharmaceutical composition ofclaim 1 wherein the acid comprises at least one of phosphoric acid,acetic acid, tartaric acid, citric acid, formic acid, malic acid andhydrochloric acid.
 5. The pharmaceutical composition of claim 2 whereinthe buffering agent comprises at least one of acetate, glutamate,citrate, tartrate, benzoate, lactate, malate, gluconate, phosphate andglycine.
 6. The pharmaceutical composition of claim 3 wherein theosmotic-adjusting agent comprises at least one of sodium chloride,calcium chloride, potassium chloride, dextrose and sodium lactate. 7.The pharmaceutical composition of claim 1 wherein the composition isprovided in a heat-sterilized container.
 8. The pharmaceuticalcomposition of claim 7 wherein the heat-sterilized container is a vial,ampoule, syringe, infusion bag or bottle.
 9. An aqueous, stable, sterilepharmaceutical composition of a thrombin inhibitor suitable forparenteral administration, substantially free from dehydrated alcoholcomprising in solution: a. 0.5 to 10 mg/mL1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban); b. 0.01 to 3 N acid to solubilize the argatroban; c. abuffering agent to maintain a solution pH about 4.5 to 5.5; and d. 1 to100 mg/ml osmotic-adjusting agent.
 10. The pharmaceutical composition ofclaim 9 comprising per 1 mL a. 1 to 10 mg1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban); b. 0.5 to 6 mg acetic acid to solubilize the argatroban;c. a buffering agent to maintain a solution pH about 4.5 to 5.5; and d.1 to 100 mg NaCl osmotic-adjusting agent.
 11. A method for preparing anaqueous, stable, sterile pharmaceutical composition of a thrombininhibitor suitable for parenteral administration, substantially freefrom dehydrated alcohol and having a pH between 3.5 and 8.5 comprisingforming an aqueous solution comprising: a. 0.1 to 10 mg/ml1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban); and b. an acid to solubilize the argatroban in a sealedcontainer and autoclaving for a period of time sufficient to render thecomposition sterile.
 12. The method of claim 11 wherein the solutionfurther comprises: c. a buffering agent and d) an osmotic-adjustingagent.
 13. The method of claim 11 wherein the solution comprises: a. 0.5to 10 mg/mL1-[5-[(aminoiminomethyl)amino]-1-oxo-2-[[(1,2,3,4-tetrahydro-3-methyl-8-quinolinyl)sulfonyl]amino]pentyl]-4-methyl-2-piperidinecarboxylic acid hydrate(argatroban); b. 0.01 to 3 N acid to solubilize the argatroban; c. abuffering agent to maintain a solution pH about 4.5 to 5.5; and d. 1 to100 mg/ml osmotic-adjusting agent.
 14. The method of claim 11 or 13,wherein autoclaving is carried out at a temperature ranging from 115 to130° C. for a period of time ranging from 5 to 40 minutes.